Honda 90

D

deel

New member
My Honda 90 misfires at low rpm and idle. Any ideas what might cause this? I have ran a new container of fuel through it with no change. Thanks,
dee
 
deel,
I would lean towards dirty carb or carbs. This happened with my Honda 40's and the fuel passages are so small that when they sit for a while they get clogged up. Unfortunately the only way to clean them is to take them apart. If you need parts I found Boats.net to be very reasonable.
 
A wild guess, assuming you have carbs, is that your low speed jets are gunked (technical term:-) up. If the engine has sat unfired for a length of time, that is quite possible.
 
Dee L, agree with the previous posts. Since I'm new here, I'll 'splain something. I'm the owner of a Honda Marine dealership in Hawaii-since 1995. We've seen our share of gunked carbs. When taking apart the carbs, look for hairline (actually smaller) cracks in the brass idle jet tube that runs from the bowl to the upper carb idle circuit. I wouldn't bother taking apart the carbs unless you have an Ultrasonic Cleaner available to you. As stated, the passages are so small and some hidden, that the UC is the only way to even come close to guaranteeing a satisfactory job. The carb kits list for less than $14 each. A complete carb set, which may be necessary if your carbs are severely corroded, will set you back $1261. MSRP. Also, in case you don't have a service manual, when cleaning the carbs, pull the entire bank off the cyl head- don't try to pull the carbs off individually. And DON'T clean the old gasket off the head or manifold with anything other than a sharp razor blade and patience.
As far as parts purchases, I'm a big fan of supporting your local dealer (big surprise there, eh?). He or she will be the one to help you out right there when you need it. Perhaps they may even let you use their UC, for a fee, of course. Just my take. Aloha, Steve.
 
nuipukawai":3w18jnoz said:
Dee L, agree with the previous posts. Since I'm new here, I'll 'splain something. I'm the owner of a Honda Marine dealership in Hawaii-since 1995.
Aloha, Steve.
Click to expand...

Steve, it will be great to have you around. Most of us can't partake in your services directly but we will certainly benefit from your sage advice.

Thanks!! And welcome to the Brats!

Charlie
 
After you get the carbs cleaned/rebuilt. You may want to run/drain all of the fuel out of the carbs. I try and run pure gas thru the engines (no ethanol). I put Stabil and Sea Foam in the fuel, at the last run, and then run this thru the engines, and all fuel lines. Then I drain each carburetor after running the fuel out (still a small amount of fuel there). Finally, I run any fuel in the lines and filter out and discard it when it is time to fire the engine back up. (I will do this even if there is a month or more between runs. I also like to run engines every week if possible.
 
Thanks for the great replies, The wife and I had the boat out two weeks ago in the Columbia river near Longview. We crossed the river at 2200 rpms, anchored and fished several hours, then pulled anchor recossed river with no misfiring it ran flawlessly. Put the boat in Columbia river near Astoria Or. then headed toward my wife's favorite fishing spot when motor started sputtering. We were running it at 2500 rpm with a snag on left and railroad trestle on the right, sure woke me up in a hurry. The motor came out of it and we continued on for about 4 or 5 miles at 4500 rpm. Ran great. Dropped anchor and fished for awhile, pulled anchor to change spots 3 or 4 times, motor ran good all the way back to launch. When throttled down it sputtered a little bit. Loaded and headed home. Flushed engine and when idling occational misfire. Have narrowed it down to cylinder number 3 counting from top down by pulling spark plug wires one at a time and listening to engine fire. I have never run ethanol in it, fuel bought from chevron dealership, have not had any problems with any other equipment ( lawn mowers, brush cutters, etc.) that have sat for awhile. Always had clean water seperator and fuel filter. This is a 2006 carburated with 150 hours on it. Thanks, Dee
 
I once had a problem with a hairline crack in a plug on a Honda. Had a devil of a time in finding it, changed out all of the plugs and, on close inspection, found the crack. It would arc periodically, causing the misfire.

Charlie
 
Hey Dee. Intermittant problems are the bane of owners and technicians. 150 hours is not a significant amount of time to require any serious maintenance, but 6 years may be. If the engine were in my shop and I could actually get it to show the symptom, and it was as you say- #3 cyl.- I'd remove the plastic rod that hooks all the choke plates together, gently start closing the #3 choke, and see if that smooths out the idle. If it does, that would indicate a lean-carb issue. If it doesn't do anything to change the problem, maybe a spark issue. Of course running the engine on a flusher instead of in the water can make things tougher to duplicate. Probably not related, but have you ever had the valves adjusted? Honda asks that they be checked at 20 hrs. and I think every 200 hrs after that. They almost never seem to need it after that until many, many hours, but it's easy to do and would eliminate a slim possibility...The idle mixture adjustment screws are of the limited travel variety- you can get the cap off by heating with a soldering iron and trying to richen the mixture a bit. Of course doing so is an EPA violation and subjects the offender to major fines. A dealer is supposed to do this to factory specs. :wink Shoot, giving away all my secrets here... :gift Aloha, Steve.
 
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